The present invention relates to magnetic disk drives and more particularly to a method for controlling the flying height of a magnetic head slider.
To raise recording densities in magnetic disk drives and consequently realize higher storage capacity and more compact drives, efforts have been made to reduce the flying height as a major means. The flying height is defined as the distance between the magnetic head slider and the magnetic disk. Reducing the distance between the read/write element and the magnetic disk's recording surface makes it possible to raise the linear recording density in the direction of rotation of the magnetic disk.
There have been prior techniques to reliably reduce the flying height of a magnetic head slider in order to raise the linear recording density in the magnetic disk's direction of rotation. One example is a system proposed in Patent Document 1 (Japanese Patent Laid-Open No. 62-250570) where a flying height adjustment structure comprising piezoelectric blocks, etc., is built into a magnetic head slider. The distance between the read/write element and the disk is finely adjusted on an individual read/write element basis by moving the read/write element perpendicularly with respect to the magnetic disk surface. In the case of a magnetic head slider proposed in Patent Document 2 (Japanese Patent Laid-Open No. 5-20635), a heat source, instead of a piezoelectric block, is provided near the read/write element of each magnetic head slider. In this magnetic head slider, the flying height is adjusted through thermal expansion by applying heat to the vicinity of the read/write element.
In a magnetic disk drive employing a magnetic head provided with such a flying height adjustment structure as mentioned above, the flying height must be reduced without deteriorating the reliability of the magnetic disk drive. The magnetic head slider must be controlled to a desired height. A method for adjusting the flying height without deteriorating the magnetic disk drive is proposed in the aforementioned Patent Document 1. In this method, the output signal from a piezoelectric block of the flying height adjustment structure provided in the magnetic head slider is monitored in order to detect contact between the magnetic head slider and the magnetic disk.
In the case of a prior art technique disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2003-168274), heating means, provided on the opposite side of the magnetic head element when viewed from the air bearing surface, is energized to reduce the magnetic spacing only when the magnetic head element is operated.